Burn-in apparatus having average voltage calculating circuit

ABSTRACT

A function test circuit inside a burn-in apparatus is mounted on a burn-in board and specifies a plurality of checked devices which operate normally. An average voltage calculating circuit calculates average voltage for test voltage applied to a plurality of checked devices specified on a mounting section. A voltage correction circuit receives the average voltage and outputs a control signal to control set voltage output from a device power supply generation circuit. Therefore, this burn-in apparatus can set the test voltage applied to the checked devices readily with high accuracy.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a burn-in apparatus to perform aburn-in test for semiconductor integrated circuit devices.

[0003] 2. Description of the Background Art

[0004] The burn-in test is performed in a checking process ofsemiconductor integrated circuit devices. An object of the burn-in testis to remove semiconductor integrated circuit devices of potential earlydefect from mass-produced semiconductor integrated circuit devices priorto shipping.

[0005]FIG. 4 is a schematic block diagram showing a configuration of aconventional burn-in apparatus.

[0006] Referring to FIG. 4, the burn-in apparatus 100 includes a body 10and a burn-in board 11. Body 10 includes a device power supplygeneration circuit 12. Device power supply generation circuit 12supplies set voltage Vs to burn-in board 11 during the burn-in test. Setvoltage Vs will be described below. Burn-in board 11 mounts a pluralityof semiconductor integrated circuit devices to be checked DUTs (devicesunder test) (a semiconductor integrated circuit device is referred to asa checked device hereinafter). Each of a plurality of checked devicesDUTs is connected to device power supply generation circuit 12 via aprotective resistance element R1.

[0007] If any of a plurality of checked devices DUTs were broken duringthe burn-in test, protective resistance element R1 prevents the brokenchecked devices DUTs from affecting voltage applied to other checheddevices DUTs.

[0008] Therefore, when burn-in apparatus 100 applies test voltage V toeach of a plurality of checked devices DUTs, the set voltage Vs outputfrom device power supply generation circuit 12 is set as follows,considering voltage drop due to protective resistance element R1;

[0009] Vs=V+iR;

[0010] wherein i is a value of current consumption of each checkeddevice DUT and R is a resistance value of protective resistance elementR1.

[0011] The value of current consumption of checked device i would bedifferent, however, depending on types of semiconductor integratedcircuit devices as checked devices DUTs, or on test conditions such astest rate during the burn-in test. As the result, set voltage Vs had tobe set for every type of checked device and every test condition.

[0012] In conventional burn-in apparatus 100, set voltage Vs was setmanually. Thus, the frequent settings of set voltage Vs made the workload heavier.

[0013] The value of current consumption of each checked device i wouldalso be different because of variations in manufacturing of respectivechecked devices DUTs. Therefore, the work load became heavier to improveaccuracy of test voltage V.

SUMMARY OF THE INVENTION

[0014] An object of the present invention is to provide a burn-inapparatus of which test voltage applied to checked devices can be seteasily with high accuracy.

[0015] A burn-in apparatus according to the present invention includes aburn-in board, a device power supply generation circuit, an averagevoltage calculating circuit, and a voltage correction circuit. Theburn-in board mounts a plurality of checked devices. The device powersupply generation circuit supplies test voltage for a burn-in test to aplurality of checked devices mounted on the burn-in board. The averagevoltage calculating circuit measures the test voltage supplied to eachchecked device and outputs the average voltage. The voltage correctioncircuit outputs a control signal to control the device power supplygeneration circuit in accordance with the average voltage.

[0016] Thus the burn-in apparatus can set the test voltage in accordancewith the average voltage calculated in the average voltage calculatingcircuit.

[0017] The voltage correction circuit preferably includes a comparator.The comparator receives the average voltage and a predetermined voltageand outputs the control signal.

[0018] Thus the burn-in apparatus compares the average voltage with thepredetermined voltage and controls the device power supply generationcircuit with this result. This can improve the accuracy of test voltageoutput from the device power supply generation circuit.

[0019] Furthermore, the burn-in apparatus preferably includes a sensingcircuit which senses a plurality of checked devices mounted on theburn-in board, and the average voltage calculating circuit measures thetest voltage supplied to each checked device sensed by the sensingcircuit and outputs the average voltage.

[0020] Therefore the burn-in apparatus can measure the test voltage forthe checked devices mounted on the burn-in board. Consequently, theaccuracy of set test voltage is improved.

[0021] Furthermore, the sensing circuit preferably senses two or moreoperable checked devices among a plurality of checked devices.

[0022] Therefore the burn-in apparatus can sense the checked deviceswhich are mounted on the burn-in board and are not broken by the test.Consequently, more accurate test voltage can be set.

[0023] It is preferred that the sensing circuit includes a functiontesting circuit to perform a function test for a plurality of checkeddevices, and the average voltage calculating circuit outputs averagevoltage in accordance with the result of the function test.

[0024] Therefore the burn-in apparatus can sense the checked devicesmounted on the burn-in board by the function test.

[0025] The average voltage calculating circuit preferably measures thetest voltage supplied to each of two or more checked devices among aplurality of checked devices and outputs the average voltage.

[0026] Therefore the burn-in apparatus can reduce the area required forwiring to measure the test voltage.

[0027] The burn-in apparatus according to the present invention measuresfor every checked device the test voltage applied to the checked devicesand calculates the average voltage. The burn-in apparatus also correctsthe test voltage using the calculated average voltage. Consequently, theburn-in apparatus can set the power supply voltage applied to thechecked devices readily with high accuracy.

[0028] The foregoing and other objects, features, aspects and advantagesof the present invention will become more apparent from the followingdetailed description of the present invention when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a schematic block diagram showing a configuration of aburn-in apparatus in an embodiment of the present invention.

[0030]FIG. 2 is a circuit diagram showing a configuration of a voltagecorrection circuit in FIG. 1.

[0031]FIG. 3 is a flowchart showing an operation of the burn-inapparatus shown in FIG. 1.

[0032]FIG. 4 is a schematic block diagram showing a configuration of aconventional burn-in apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Embodiments of the present invention will be described in detailwith reference to the drawings. In the drawings, the same orcorresponding parts have the same reference characters and thedescription will not be repeated.

[0034]FIG. 1 is a schematic block diagram showing a configuration of aburn-in apparatus in an embodiment of the present invention.

[0035] Referring to FIG. 1, the burn-in apparatus 200 includes a body 20and a burn-in board 30 mounting a plurality of checked devices.

[0036] Burn-in board 30 includes mounting sections 1-n (n is a naturalnumber) which mount a plurality of checked devices DUTs.

[0037] Mounting section 1 can mount m (m is a natural number) checkeddevices DUT1-DUTm. Each mounted checked device DUT is connected to adevice power supply generation circuit 13 inside body 20 via aprotective resistance element R1. Each of a plurality of checked devicesDUT1-DUTm mounted on mounting section 1 also receives test patternsignal output from body 20. The test pattern signal will be describedbelow. Mounting section 1 includes a plurality of sockets (not shown) tomount a plurality of checked devices DUT1-DUTm.

[0038] Each of a plurality of checked devices mounted on mountingsection 1 is also connected to an average voltage calculating circuit 26inside body 20. Average voltage calculating circuit 26 will be describedbelow.

[0039] A plurality of checked devices mounted on mounting sections 2-nare not connected to average voltage calculating circuit 26. Otherconfigurations of mounting sections 2-n are the same as mounting section1 and the description will not be repeated here.

[0040] As the result, the number of checked devices mountable on burn-inboard 30 is n×m.

[0041] Body 20 includes a device power supply generation circuit 13, afunction test circuit 21, an average voltage calculating circuit 26, avoltage correction circuit 27, and a control circuit 28.

[0042] Function test circuit 21 performs function test for a pluralityof checked devices mounted on burn-in board 30. Function test circuit 21includes a timing generation circuit 22, a pattern generation circuit23, a driver and comparator 24, and a test result processing circuit 25.

[0043] Timing generation circuit 22 outputs a reference signal whichwill be a base for the function test. The reference signal output fromtiming generation circuit 22 determines a cycle time of the functiontest.

[0044] Pattern generation circuit 23 outputs a preset test patternsignal in synchronization with the reference signal output from timinggeneration circuit 22.

[0045] Driver and comparator 24 outputs the test pattern signal to aplurality of checked devices DUTs mounted on burn-in board 30. It alsoreceives the signal output from each checked device DUT which receivedthe test pattern signal, and determines whether the each checked deviceoperated normally or not, and then outputs the determination result totest result processing circuit 25. Each of a plurality of checkeddevices mounted on burn-in board 30 is specified, and the determinationis done for each checked device.

[0046] Test result processing circuit 25 stores the determinationresults output from driver and comparator 24. Test result processingcircuit 25 stores the determination results corresponding to a pluralityof checked devices DUT1-DUTm.

[0047] Average voltage calculating circuit 26 receives the determinationresults stored in test result processing circuit 25, measures the testvoltage V applied to a plurality of checked devices which were mountedon mounting section 1 and operated normally, and calculates the averagevoltage Vave of the measurement results. Average voltage calculatingcircuit 26 outputs the calculated average voltage Vave to voltagecorrection circuit 27.

[0048]FIG. 2 is a circuit diagram showing a configuration of the voltagecorrection circuit in FIG. 1.

[0049] Referring to FIG. 2, voltage correction circuit 27 is configuredwith a comparator.

[0050] Referring to FIG. 2, voltage correction circuit 27 includesN-channel MOS transistors QN1, QN2 and P-channel MOS transistors QP1,QP2. Sources of transistors QP1 and QP2 are both connected to internalpower node 40. Gates of transistors QP1 and QP2 are connected togetherand further, transistor QP1 is diode-connected.

[0051] Transistor QN1 has its drain connected to the drain of transistorQP1 and transistor QN2 has its drain connected to the drain oftransistor QP2, respectively. Sources of transistors QN1 and QN2 areboth connected to constant-current source 60. Reference voltage Vref isinput to a gate of transistor QN1 and average voltage Vave is input to agate of transistor QN2, respectively, and control signal Vout is outputfrom output node A1 which is a connection point of transistor QP2 andtransistor QN2.

[0052] Reference voltage Vref is output from control circuit 28 whichwill be described below.

[0053] Constant-current source 60 is connected to ground node 50.

[0054] Returning to FIG. 1, device power supply generation circuit 13outputs set voltage Vs to supply test voltage V to a plurality ofchecked devices DUTs mounted on burn-in board 30.

[0055] In addition, device power supply generation circuit 13 receivesthe control signal Vout and controls a value of test voltage V to beoutput.

[0056] Control circuit 28 stores a plurality of different burn-in testprograms. Control circuit 28 selects a burn-in test program and outputsto device power supply generation circuit 13 the information of testvoltage V to be applied to checked devices DUTs during the burn-in test.It also outputs the reference voltage Vref corresponding to the selectedburn-in test program to average voltage correction circuit 27.

[0057] An operation of burn-in apparatus 200 having the above-mentionedconfiguration will now be described.

[0058]FIG. 3 is a flowchart showing an operation of burn-in apparatus200 shown in FIG. 1.

[0059] Referring to FIG. 3, control circuit 28 in burn-in apparatus 200first selects a test of test NoT=1 (step S1). Herein, test NoT (T is anatural number) indicates a number for each of a plurality of differentburn-in tests performed in burn-in apparatus 200. Burn-in apparatus 200performs burn-in test of every test No for a plurality of checkeddevices DUTs mounted on burn-in board 30. Programs of multiple burn-intests having test NoT are stored in a hard disk (not shown) insidecontrol circuit 28 of FIG. 1.

[0060] In step S1, control circuit 28 instructs device power supplygeneration circuit 13 to supply test voltage V which will be applied toeach checked device DUT for test No 1. Test voltage V is preset forevery test No and the data of the test voltage V for each test No isprestored in hard disk inside control circuit 28.

[0061] Burn-in apparatus 200 then performs a function test for aplurality of checked devices DUTs on burn-in board 30 (step S2). Thefunction test is, for example, a march pattern test.

[0062] At this time, function test circuit 21 outputs test patternsignal. Furthermore, it uses signal output from each checked device DUTthat has received the test pattern signal to determine whether eachchecked device operated normally or not, and stores the results in testresult processing circuit 25 inside function test circuit 21. With theoperation of step S2, burn-in apparatus 200 can specify the checkeddevice DUT which is mounted on burn-in board 30 and is not broken.

[0063] Then, device power supply generation circuit 13 outputs setvoltage Vs to apply test voltage V to each checked device DUT. Averagevoltage calculating circuit 26 inside burn-in apparatus 200 measures thetest voltage V actually applied to checked devices DUTs using thedetermination results stored in test result processing circuit 25 (stepS3).

[0064] More specifically, average voltage calculating circuit 26 obtainsdetermination results of a plurality of checked devices DUT1-DUTm onmounting section 1 from test result processing circuit 25. From theobtained determination results, average voltage calculating circuit 26specifies a plurality of checked devices DUTs which are mounted onmounting section 1 and operated normally. Then, average voltagecalculating circuit 26 measures test voltage V applied to a plurality ofchecked devices DUTs which are specified.

[0065] Thereafter, average voltage calculating circuit 26 calculatesaverage voltage Vave of test voltage measured in step S3 (step S4).Average voltage calculating circuit 26 outputs the calculated averagevoltage Vave to voltage correction circuit 27.

[0066] Voltage correction circuit 27 receives the average voltage Vaveand outputs the control signal Vout (step S5). Reference voltage Vref isoutput from control circuit 28 and the value differs for every test No.Voltage correction circuit 27 outputs control signal Vout to devicepower supply generation circuit 13.

[0067] Device power supply generation circuit 13 then determines whetherthe voltage value of received control signal Vout is within tolerance ornot (step S6). Tolerable range of control signal Vout is prestored indevice power supply generation circuit 13.

[0068] If the determination result of device power supply generationcircuit 13 indicates that the received control signal Vout is withintolerance, burn-in apparatus 200 will perform burn-in test of test No 1(step S7).

[0069] After the test is completed, control circuit 28 selects testNoT=2 (step S8), and burn-in apparatus 200 restarts the operation fromstep S2.

[0070] On the other hand, if device power supply generation circuit 13determines that the received control signal Vout is out of the tolerancein step S6, device power supply generation circuit 13 corrects setvoltage Vs corresponding to control signal Vout (step S9). Correctionamount of set voltage Vs corresponding to control signal Vout isprestored in device power supply generation circuit 13, and device powersupply generation circuit 13 corrects set voltage Vs based on thecorrection amount determined with received control signal Vout.

[0071] After the correction of set voltage Vs in step S9, the operationof burn-in apparatus 200 returns to step S3. Correction operation ofstep S9 will be repeated until the voltage level of control signal Voutoutput from voltage correction circuit 27 is included in the tolerance.

[0072] Although the present invention has been described and illustratedin detail, it is clearly understood that the same is by way ofillustration and example only and is not to be taken by way oflimitation, the spirit and scope of the present invention being limitedonly by the terms of the appended claims.

What is claimed is:
 1. A burn-in apparatus, comprising: a burn-in boardon which a plurality of checked devices are mountable; a device powersupply generation circuit supplying test voltage for burn-in test tosaid plurality of checked devices mounted on said burn-in board; anaverage voltage calculating circuit measuring said test voltage suppliedto each of said plurality of checked devices and outputting an averagevoltage; and a voltage correction circuit outputting control signal tocontrol said device power supply generation circuit in response to saidaverage voltage.
 2. The burn-in apparatus according to claim 1, whereinsaid voltage correction circuit includes a comparator receiving saidaverage voltage and predetermined voltage and outputting said controlsignal.
 3. The burn-in apparatus according to claim 1, furthercomprising a sensing circuit sensing said plurality of checked devicesmounted on said burn-in board; wherein said average voltage calculatingcircuit measures said test voltage supplied to each of said plurality ofchecked devices sensed by said sensing circuit and outputs said averagevoltage.
 4. The burn-in apparatus according to claim 3, wherein saidsensing circuit further senses two or more operable checked devicesamong said plurality of checked devices.
 5. The burn-in apparatusaccording to claim 4, wherein said sensing circuit includes a functiontesting circuit performing a function test for said plurality of checkeddevices; and said average voltage calculating circuit outputs saidaverage voltage in response to the result of said function test.
 6. Theburn-in apparatus according to claim 1, wherein said average voltagecalculating circuit measures said test voltage supplied to each of twoor more checked devices among said plurality of checked devices andoutputs said average voltage.